The singer/fashion mogul announced she and husband Eric Johnson were adding one more to their brood on Instagram Tuesday. In the first of two posts starring the couple's kids – Maxwell Drew, 6 and Ace Knute, 5 – Simpson, 38, simply wrote "SURPRISE..."

In the next image, her kids appear mesmerized by a sea of pink balloons. Adding some context, Simpson shared news of the new baby. "This little baby girl will make us a family of five," she wrote. "We couldn’t be happier to announce this precious blessing of life."